Apparatus for aerating liquids in a tank having wave attenuator

ABSTRACT

A surface aerator in a tank creates horizontally directed surface flow that forms waves as the flow progresses through the tank and impinges upon the tank wall. At least one substantially horizontal baffle is mounted adjacent the inner wall of the tank adjacent or subjacent the liquid level and is positioned at a point of high wave amplitude to attenuate the waves by eliminating the vertical energy component thereof. The baffle may have a passage therethrough for circulation of liquid.

United States Patent [191 Auler July 29, 1975 1 APPARATUS FOR AERATING LIQUIDS IN A TANK HAVING WAVE ATTENUATOR [75] Inventor:

[73] Assignee: Passavant-Werke Michelbacher Huette, Germany [22] Filed: Feb. 26, 1974 21 Appl. No; 445,897

Herbert Auler, Aarbergen, Germany [30] Foreign Application Priority Data Mar. 13, 1973 Germany 2312476 {52] US. Cl. 261/91; 61/3; 61/49 [51] Int. Cl. B01F 3/04; BOIF 7/16 [58] Field of Search 261/123, 91, 92,110,112, 261/113, 84, 93,120;61/3, 5, 49,];

[56] References Cited UNITED STATES PATENTS 1,497,425 6/1924 Ames et al 261/91 Robertson 261/91 Auler 261/91 Primary Examiner-Tim R. Miles Assistant ExaminerGreg0ry N. Clements Attorney, Agent, or Firm-Woodford R. Thompson, Jr.

[57] ABSTRACT A surface aerator in a tank creates horizontally directed surface flow that forms waves as the flow progresses through the tank and impinges upon the tank wall. At least one substantially horizontal baffle is mounted adjacent the inner wall of the tank adjacent or subjacent the liquid level and is positioned at a point of high wave amplitude to attenuate the waves by eliminating the vertical energy component thereof. The baffle may have a passage therethrough for circulation of liquid.

9 Claims, 3 Drawing Figures APPARATUS FOR AERATING LIQUIDS IN A TANK HAVING WAVE ATTENUATOR BACKGROUND OF THE INVENTION This invention relates to apparatus for aerating liquid, and more particularly to such apparatus which comprises an aeration tank having at least one rotary surface aerator arranged thereon. The horizontal liquid flow caused by rotation of the aerator creates horizontally directed surface flow which impinges at an angle upon the tank wall. Heretofore, one or several substantially horizontal baffles have been mounted on the tank wall or in close proximity thereof, at the liquid level or immediately below the liquid level within the range of impingement of the horizontal liquid flow. Such apparatus is disclosed in my US. Pat. No. 3,767,175 dated Oct. 23, 1973. Such baffling means reduce the propagation of waves in the tank by skimming off the crests of the waves thereby preventing them from being reflected by those parts of the tank walls provided with the baffles.

Heretofore, the assumption has been that the baffling means would be most effective if stationed at a point where relatively heavy horizontal streams caused by the aerator impinge upon the tank wall. Accordingly, in a rectangular tank with a central vertical-shaft surface aerator, the baffling means would have to be positioned midway of the side wall.

BRIEF SUMMARY OF INVENTION In accordance with my invention, I improve the baffling effect by an unexpected arrangement of the baffling means. I have found that the efficiency of the baffling means will be greatly improved if the baffles are positioned at points of high wave amplitude in a polygonal tank, such as a rectangular tank. The points of high wave amplitude do not coincide with the zones of impingement of the heaviest horizontal liquid flow. Preferably, the baffling means is positioned in at least one corner of the tank. Preferably, the baffling means has a flow passage therethrough for circulation of liquid.

DESCRIPTION OF THE DRAWINGS The invention is described by reference to the specific embodiments illustrated in the accompanying schematic drawing showing an aeration tank equipped with the baffling means of my invention, wherein:

FIG. I is a sectional view taken along the line 1--1 of FIG. 2;

FIG. 2 is a top plan view; and,

FIG. 3 is a fragmental, plan view of one corner of the tank showing a modification.

DETAILED DESCRIPTION Referring now to the drawings for a better understanding of my invention, I show a rectangular aeration tank 1 which is equipped with a conventional, centrally disposed surface aerator 2 that rotates about a vertical axis and causes a horizontal spiral flow circulation of liquor inside the tank, as indicated by arrows 3.

I show baffling means mounted in each of two diagonally opposed corners of the tank 1. Each baffling means consist of a horizontally disposed plate 4 or the like, positioned adjacent liquid level, which is intended to mean at liquid level or immediately below liquid level. In plan view each baffle plate 4 is shown as being in the shape of a right-angled, equal-sided triangle which covers the entire tank corner. Each baffle plate 4 is provided with an open flow passage 5 which may be in the form of a narrow slit extending between the upper and lower surface and parallel to the front edge of the baffle plate 4. These open passages 5 may take up at least 10% of the total surface area of the baffle means 4. Instead of the narrow slit the passages 5 may consist of a plurality of single holds. The liquor will circulate upwardly or downwardly through the passages 5, depending on the prevailing flow conditions, so that the reduced flow passages will greatly reduce wave intensity.

When the surface aerator 2 is in operation, it creates horizontally directed surface flow that forms into waves as the flow progresses through the tank 1. The waves thus formed impinge upon the baffle plates 4 and are divided or split horizontally, so that a reflection by the tank wall is largely eliminated within the zone of the baffling means. It was an pnexpected fact that even relatively small baffle plates 4 will suffice to this end and will suppress wave formation not only in the corners where the baffle plates 4 are positioned but throughout the entire tank 1. For a tank measuring approximately by 45 feet, two baffle plates 4 having a hypotenuse or front edge of approximately 10.5 feet will suffice completely to suppress wave formation throughout the tank and prevent the surface aerator 2 from vibrating.

From the foregoing, it will be seen that the baffle plates 4 do not have to be installed in all four corners of the tank since the waves can be suppressed effectively by the installation of baffle plates in two diagonally opposed corners of the tank. Preferably, the front edge of each baffle plate 4 is so positioned that it will extend diagonally across the corner of the tank, as shown. Also, as mentioned above, surprisingly good results are obtained by employing baffling means of extremely small surface area as compared to the total tank surface.

In FIG. 3 of the drawings I show the flow passages through each baffle plate 4 as being in the form of a plurality of separate passages 5 instead of the narrow slit 5 shown in FIG. 2.

While] have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What I claim is:

1. In apparatus for aerating liquids in a rectangular aeration tank having at least one surface aerator mounted for rotation therein which creates horizontally directed surface flow that forms into waves as the flow progresses through the tank and impinges at an angle upon the tank wall:

a. at least one substantially horizontal baffle mounted adjacent the inner wall in a corner of said tank adjacent the liquid level thereof and positioned at a point of high wave amplitude.

2. Apparatus as defined in claim 1 in which said baffle is mounted subjacent the liquid level of the tank.

3. Apparatus as defined in claim 1 in which a said baffle is mounted in each of at least two diagonally opposed corners of the tank.

4. Apparatus as defined in claim 1 in which the front edge of said baffle extends diagonally across the corner of the tank in which it is positioned.

5. Apparatus as defined in claim 4 in which said baf fle is in the shape of a triangle, covering the entire corner area.

6. ln apparatus for aerating liquids in a polygonal aerb. there being at least one open flow passage through each said baffle for the circulation of liquid in an upward and a downward direction.

7. Apparatus as defined in claim 6 in which said open ation tank having at least one surface aerator mounted flow passage takes up at least 10% of the total surface for rotation therein which creates horizontally directed surface flow that forms into waves as the flow progresses through the tank and impinges at an angle upon the tank wall:

a. at least one substantially horizontal baffle mounted adjacent the inner wall of said tank adjacent the liquid level thereof and positioned at a point of high wave amplitude, and

area of each said baffle.

8. Apparatus as defined in claim 7 in which said open flow passage is a slit in said baffle extending parallel to the front edge thereof.

9. Apparatus as defined in claim 7 in which said open flow passage comprises a plurality of separate passages through said baffle. 

1. In apparatus for aerating liquids in a rectangular aeration tank having at least one surface aerator mounted for rotation therein which creates horizontally directed surface flow that forms into waves as the flow progresses through the tank and impinges at an angle upon the tank wall: a. at least one substantially horizontal baffle mounted adjacent the inner wall in a corner of said tank adjacent the liquid level thereof and positioned at a point of high wave amplitude.
 2. Apparatus as defined in claim 1 in which said baffle is mounted subjacent the liquid level of the tank.
 3. Apparatus as defined in claim 1 in which a said baffle is mounted in each of at least two diagonally opposed corners of the tank.
 4. Apparatus as defined in claim 1 in which the front edge of said baffle extends diagonally across the corner of the tank in which it is positioned.
 5. Apparatus as defined in claim 4 in which said baffle is in the shape of a triangle, covering the entire corner area.
 6. IN APPARATUS FOR AERATING LIQUIDS IN A POLYGONAL AERATION TANK HAVING AT LEAST ONE SURFACE AERATOR MOUNTED FOR ROTATION THEREIN WHICH CREATES HORIZONTALLY DIRECTED SURFACE FLOW THAT FORMS INTO WAVES AS THE FLOW PROGRESSES THROUGH THE TANK AND IMPINGES AT AN ANGLE UPON THE TANK WALL: A. AT LEAST ONE SUBSTANTIALLY HORIZONTAL BAFFLE MOUNTED ADJACENT THE INNER WALL OF SAID TANK ADJACENT THE LIQUID LEVEL THEREOF AND POSITIONED AT A POINT OF HIGH WAVE AMPLITUDE, AND B. THERE BEING AT LEAST ONE OPEN FLOW PASSAGE THROUGH EACH SAID BAFFLE FOR THE CIRCULATION OF LIQUID IN AN UPWARD AND A DOWNWARD DIRECTION.
 7. Apparatus as defined in claim 6 in which said open flow passage takes up at least 10% of the total surface area of each said baffle.
 8. Apparatus as defined in claim 7 in which said open flow passage is a slit in said baffle extending parallel to the front edge thereof.
 9. Apparatus as defined in claim 7 in which said open flow passage comprises a plurality of separate passages through said baffle. 